Electric motor speed control system



March 25, 1952 TURNER, JR 2,590,356

ELECTRIC MOTOR SPEED CONTROL SYSTEM Original Filed April 10, 1945 5Sheets-Sheet l RECORDER j 2/ [7 SPEED CON TROL /ascavs/z PROJEC7Y'O7ISAMPLIFIER I gig f6 L l prza/ecrorz /NI/EN7UR EDWIN E. TURNER, J12.

March 25, 1952 E. E. TURNER, JR

ELECTRIC MOTOR SPEED CONTROL SYSTEM 5 Sheets-Sheet 2 Original FiledApril 10, 1945 lNVENTOR sow/1v E nnav BY ZZ ENE Y March 25, 1952 E. E.TURNER, JR 2,590,356

ELECTRIC MOTOR SPEED CONTROL SYSTEM Original FiledApril 10, 1945 5Sheets-Sheet 3 J INVENRDR Eownv 5. 7Z//?NEP, J/a

March 25, 1952 E. E. TURNER, JR 2,590,355

ELECTRIC MOTOR SPEED CONTROL SYSTEM Original Filed April 10, 1945 5Sheets-Sheet 4 BY RNEY mN. mwom os RR N V OE mm E -Am n n W m H m mow OW III: W I II|-|.|H/!\.|l. l |.\l| 1 II. I lllilllllll I I. III! Illa||||L W whwnnnwl nmnn lw u l lflw l n nwm nww l lwmmw nl||I|||II|II|I EW h M? 4 ||H| Nw W W 7 mm L h i U ml 0 Q m "I \J h H 1Q O U QTIJ w. fi\W# H H w U N%,L ll" U llllllllllll |....||I||l|I|| U u 5 H m v mm m O m.Q& P .v v P h M" h m. R w mm 3 E R R March 25, 1952 E. E. TURNER, JR

gLEcTRIc MOTOR SPEED CONTROL SYSTEM Original Filed April 10, 1945 5Sheets-Sheet 5 INVENTOI? EDWIN E. TURNER, J12

Patented Mar. 25, 1952 ELECTRIC MOTOR SPEED CONTROL SYSTEM Edwin E.Turner, Jr., West Roxbury, Mass., as-

signor, by mesne assignments, to Raytheon Manufacturing Company, acorporation of Delaware Original application April 10, 1945, Serial No.587,633. Divided and this application May 25, 1949, Serial No. 95,301

Claims. (Cl. 318-318) This is a division of my copending application,Serial No. 587,633, filed April 10, 1945, now Patent Number 2,475,363.

The present invention relates to a signaling system for the detection ofunknown objects and in particular to a method of detection of objects ina water medium by the use of compressional waves.

The present invention also has special applications for military uses inproviding a means of detecting enemy submarines or surface vessels. Inthis respect the system, when installed on a vessel, provides means ofautomatic and continuous search in all sectors about the vessel toprovide for the detection and determination of direction of objects byobservation of sounds produced by the object and the detection anddetermination of both direction and distance of an object by echoranging, within the operational .for the same sector.

that observations are made at approximately a constant range. In thisrespect the system is similar to that disclosed in the application ofEdward W. Smith, Serial No. 343,977, filed July 5, 1940, now PatentNumber 2,505,587.

The sequence of operations during the ranging may be any one of a numberof combinations. In one of the preferable arrangements in accordancewith my invention I first continuously transmit a signal in the forwardsector of the vessel, which may for example be 180, by the rotationthrough the sector of a directional high frequency sound projector whichmay be of the magnetostrictive, piezoelectric, electromagnetic orelectrodynamic type, and then automatically change the system over fromtransmitting to receiving The same device may be used for sending as forreceiving, in which case the projector, after it has finished sendingwhile range of the system. rotating through the first 180, may bepermitted The apparatus employed in the present inven- While silent torotate through the aft 180. and tion has many new and useful featureswhich on then. the System having automatically Changed the whole tend toprovide for almost all conov r to r pti n, t p j t r begins to p k utingencies which may occur. As a vessel is norr fl ed ign ls in the ectr in which h r mally proceeding on its chosen course, the sysinal signalwas sent. This results in a time intern will range fore and aft of thevessel at a t a b tw n t a g a d receiving in y chosen distance, whichis to say that any object given direction qua t th ti it tak s th p orobstacle appearing at that distance will be dej to rotate and W c timeinterval tected and its direction determined. As a deh refore determinesthe distance at which the tected. object and the vessel approach oneanran i is t b d n that s. only j s at that other, the apparatus willcontinue to range on distance or multiples thereof will be detected. theobject giving both its distance and direction The speed of rotation ofthe proj or h e o as the distances decrease and the courses change.controls this ranging distance. It is also possi- In the event that theobject is no longer picked ble to arrange the system so that after theproup, then the ranging zone, in order again to de jector has receivedin the forward 180, it will tect the object, will automatically increaseagain begin to transmit in the aft 180 and similarly until a maximumrange setting has been arrived one turn later begin to receive in theaft 180. at, whereupon unless the apparatus is set to con- Again, thesystem can be so arranged that at tinue to range for the maximumdistance, the the end of the 180 period of reception in the aft rangingwill again change to a distance close to sector transmission in theforward range will the vessel and then again gradually increase. againoccur, with the cycle of ranging alter- This, with the system set forautomatic ranging, nately forward and aft repeating itself from thiswill continue to occur as long as desired. point. Also by the use ofareceiving projector In the use of the system for ranging in a whosebeam is 180 from the transmitting prowater medium, as, for instance, ina vessel under .i cto i s possible t transmit for y a way, atransmitting and receiving unit having directional beam characteristicsmay be employed which may be rotated continually about 360 around thewhole horizon. In this case a signal will be transmitted during therotation of the projector or transmitter through a given sector and thenthe receiver will be rotated through the same sector at the desired timeinterval later. The time of rotation for successive revolutions may besubstantially the same or vary little so revolution and immediatelyreceive through the same angle on the receiving projector with no hiatusbetween the cessation of transmission and the beginning of reception.

When the switches in my system are set for automatic ranging, rangingcommences at a distance close to the vessel and gradually increases tothe maximum range, whereupon ranging is quickly brought back again tothe inner range close to the vessel. This is accomplished by anautomatic control of the speed of rotation of the projector ashereinafter described.

The present system preferably provides a recording mechanismforrecording each individual observation of a reflected signal on asheet which travels in a straight path at a chosen rate which may beconstant or varied as desired. The

incoming signal representing the echo from the unknown object isrecorded both as to distance and direction with reference to a centerpoint. For this purpose the recording stylus which produces the recordis rotated about a center point in synchronism with the rotation of theprojector and receiver so that the stylus direction from the centerpoint at the instant that the record is made is the direction of theobject; moreover, the stylus is positioned radially from the centerpoint so that its distance from the center point gives a measure of thedistance of the object. The traces of successive observations of theobject may be produced as a straight line for an indication of acollisioncourse between the object and the observing vessel.

A clearer understanding of the operation of the system and its manyapplications and advantages together withits novelty over the art willbe obtained and appreciated from the description below which is given inconnection with the accompanyingdrawings showing an embodiment of theinvention. In the drawings:

Fig. 1 shows the system as a whole in a simplified schematic generallayout;

Figs. 2, 3, 4 and together represent a complete schematic wiring diagramof the system. Fig. 2 should be held with the long dimension of thesheet vertical and includes primarily the projector, its rotatingmechanism and its power supply; Fig. 3 continues from the top of Fig. 2when the sheet of Fig. 3 is placed horizontally above Fig. 2 with thearrows marked to Fig. 2 opposite the arrows on Fig. 2 marked to Fig. 3and includes primarily the speed control unit; the diagram is furthercontinued in Fig. 4, placed horizontally above Fig. 3 with the arrowsmarkedto-Fig. 3opposite the arrows on'Fig. 3 marked to Fig. 4:and Fig. 4includes primarily the receiver amplifier; and Fig. 5, heldhorizontally, continues'and completes the diagram when the arrow at theleft marked to Fig. 4 is placed opposite the arrow at the right on Fig.4, marked to Fig. 5 and includes primarily the recorder instrument andcontrol switches.

Fig. 1 of the drawings indicates the apparatus schematically insimplified form. There is a compressionalwaveprojector 1, whichcorresponds to the same numbered element shown in Fig. 2. This may beprovided with two separate projector units if desired, of the sameconstruction, or of different construction mounted back to back witheach other as indicated diagrammatically in Fig. 2, or for some purposesa single unit may be sufiicient. As shown in Fig. 2, the projector unit2 on the right may be a piezoelectric crystal projector, and the unit 3-on the left a magnetostrictive projector. Both of these units havedirective characteristics for transmitting and receiving wave energy ina narrow band or solid anglewhose axis is horizontal or, moregenerally'stated, in a plane perpendicular to the rotating axis of thedevice. However, it should be understood that only a singleunit isessential, although both units may be used. I

When installedupon a, vessel the device I may project from the bottom ofthe vessel and be ro-. tated by means of a shaft 4 driven by a gear 5through its worm 6 which is turned by means of a driving motor 1 whosespeed is controlled by a speed control unit I6 as described below. InFig. 1, the gear 5 is illustrated diagrammatically in a verticalposition so as to show that it meshes with the worm 6 actually, however,it is mounted concentric with the shaft 4.

This driving motor 1 corresponds to the elements numbered 1a and If inFig. 2. The motor I is attachedby its shaft to the worm 6 and to thearmature shaft of the self -synchronous motor 8 so that its rotor 81(Fig. 2) is always mechanlcally connected to the armature 1a of themotor 1. One of the projector units, e. g. the magnetostrictive unit 3,may be used as a transmitting unit and may be energized by a highfrequency driving circuit by means of a power supply ll (Fig. 1) whichmay be called the projector power supply. The circuit arrangements ofthis power supply appear in detail in the upper portion of Fig. 2. Theother projector unit, in this case the crystal unit 2, may be used as'areceiving unit. While receiving, the signal picked up is passed to areceiver amplifier M. The circuit arrangements of the receiver amplifierare shown in detail in Fig. 4. Thus in the circuit, as arranged in Fig.2 of the drawings, the left half 3 of the projector is connected to theprojector power supply I I over the shielded cable l2. The right half 2of the projector is connected to cable l3 which passes upward at theextreme left of Fig. 2 whence it continues through Fig. 3, at theextreme left and into Fig. 4, in the same relative position, where it isapplied to the receiver amplifier Hi.

If desired a switching arrangement may be employed to operate theprojector units in the reverse manner; that is to say, the projectorwhich receives may act as a transmitter and the one which transmits mayact as a receiver.

Referring again to Fig. 1, besides the elements already mentioned, thereare also used a recorder and operational control unit 15 and anelectronic motor speed control unit 16. The circuit arrangements of therecorder and control unit 15 are shown in detail in Fig. 5. Themechanical arrangements of a suitable recorder are shown and describedin detail in the parent of this application, Serial No. 587,633, filedApril 10, 1945, now Patent No. 2,475,363, dated July 5, 1949. Thecircuit arrangements of the motor speed control unit 16 are shown indetail in Fig. 3.

In the recorder and control unit ,I 5, a record is made by a stylusI'Iwhich is carried on a selfadjustable ribbon or band 18. The stylus llmarks on a continuously moving recording paper be neath it. The stylusassembly, which includes the ribbon l8 and other elements which will bedescribed, is rotated by means of the self-synchronous motor 2 I whichis driven by the self -synchronous generator 8. The result of this isthat the stylus assembly rotates in complete synchronism with therotation of the projector I, .so that the position of the stylus withrespect to-the axis of rotation of the stylus assembly is relatively thesame as the direction in which the projector points or receives at theinstant that the record is made.

The electronic control unit 16 is arranged to control the speed of themotor I so that both the projector l and the stylus assembly 22 willrotate at the same desired speed. Other purposes of the control unit Itare to provide automatic control of the speed dependent upon the rateatwhich reflected signals or echoes are received and to provide controlalso of the speed by means of range-control settings in the unit [5.

The projector is keyed for transmission by means of a cam key 23, whoseoperation will be explained more fully later, during a selected sectorof the projectors rotation corresponding to a sector of rotation of thestylus. The time interval between the end of transmission and thebeginning of reception over the sector being searched or observed thusdepends upon the time interval it takes for the projector to rotatearound to the initial position for reception. It follows that the rangefrom which an echo will come back and be received by the projectordepends upon the time it takes for the projector to make a completerevolution, when a single projector unit is used for both transmissionand reception. This may be explained simply by saying that if for halfof a revolution of the projector a signal has been sent out. then whenthe projector is in position to receive (on the beginning of the nextrevolution) the time elapsed will be the time of a single revolution. Ifthis, we assume, is four seconds, and if further we assume that thespeed of sound in water is 4800' per second, then a returning echo willcome from a distance of approximately 9600, so that for this speed ofrotation of the projector and of the stylus assembly, observations willbe made of objects at that distance, An arrangement is employed in thestylus assembly which is described in the aforementioned parentapplication whereby the stylus [1 remains a distance out from its axisof rotation proportional to the range which is being observed. It willbe noted from the above discussion that the speed of rotation of theprojector determines the range observed and the stylus mechanismoperable in a proportional relation with such speed of rotation providesa measurement of the range with respect to the stylus center ofrotation. It should be noted here that it has been found expedient forcertain ranges of operation, namely, short ranges, to modify thisarrangement by utilizing one projector for transmission and anotherprojector whose beam axis is opposite in space to that of the firstprojector by 180 for reception, transmitting on the transmittingprojector for half a revolution and receiving on the receiving projectorfor the subsequent half revolution. Under these conditions the speed ofrotation is obviously halved for the range as above described. It hasbeen found that the first-mentioned arrangement, namely, the use of thesame projector for transmission and reception, is to be preferred forlong range echoes because the hiatus between the cessation oftransmission after the first half revolution and the beginning ofreception after the first full revolution serves as an interval to allowthe local reverberations to die out before the recording point is madeactive. The second condition where separate transducers are used fortransmission and reception can be made to operate well at the shorterranges because at these ranges the echoes are suiiiciently above thereverberation level so that reverberations may be eliminated by a simplereduction of gain. The reverberations which bother under theseconditions are those occurring immediately after the cessation oftransmission and are received on the receiving projector even though itsbeam axis is 180 degrees away from the transmitting beam axis by virtueof local diffraction around the projector. It must be pointed out thatthis system of scanning echo ranging has certain unique advantages withrespect to reverberations not possessed by other systems, namely, thatat any given speed of rotation, that is to say at any given range,reverberations are being received only from that range. Thus automaticelimination of short time reverberations at ranges between the targetand the ship is effected. It is these reverberations which are sotroublesome with the usual searchlight type of echo ranging in depthalong a single line.

Certain functions and operations of the circuits; will now be describedin connection with the circuit diagram in Figs. 2 to 5. The highfrequency power supply or oscillator for furnishing the desiredoscillatory frequency to the projector is the unit H. The oscillator llmay be energized from the shipssupply connected to the conductors 24,25, Fig. 2, and carried on the lines 23, 24, 25 which connect to thetransformers 25 and 21 whose secondaries are connected to the rectifiers28 and 29. The output of these rectifiers is applied to theanode-cathode circuit of a conventional oscillator including theoscillatory tubes 30 and 3|.

However, the rectifier output is applied to the oscillator through atime delay circuit composed of a choke 32, a condenser C32 and aresistance 33. The result of this arrangement is that the point 34 atthe right end of the choke as viewed in Fig. 2 has a negative voltageapplied to it before the rush of power is applied to the projector. Thishigh negative voltage of the point 34 is applied through the resistance33 and the cable 35 which passes through the circuit of Fig. 3 to Fig. 4where it is connected to the screen grids 50', 5| of tubes 50, 5|,respectively, and to screen grids 31, 38 of the tubes 39, 40,respectively, in the receiving-amplifying circuit. The tubes 50 and 5|are in the first amplifier stage, while tubes 39 and 40 are in thesecond stage of the amplifier. Thus when the power supply H is keyed,there is such a high negative bias placed upon the amplifier tubesduring signal transmission that the receiving circuit automaticallybecomes blocked and no disturbance due to the directly transmittedsignal will affect the indicating circuit during the transmission of thesignal. This protects the receiving circuit in such a manner that whenthe negative potential is later slowly relieved, as will be explainedlater, the circuit is ready in time to receive and indicate any impulsewhich might be picked up. It will be noted that the tubes 50, 5| andtubes 39, 40, respectively, are arranged in push-pull circuits. This isdone so that the surge, produced in each half of the push-pull circuitsby the sudden application of the negative voltage on the grids, will bebalanced out with the result that no voltage will appear at theamplifier output terminals.

When transmission stops, the negative potential at the point 34 isremoved. The screens 50', 5| and 31, 38 in the tubes 50, 5| and 39, 40.respectively, will thereafter come up to a positive potential relativelyslowly because of a time constant circuit made up of the condenser 42and the resistance 43 (Fig. 4). This is aided by the use of one side ofa rectifier 44, connected to the time delay circuit through lead 45, andarranged in such a way as to permit the rapid application of thenegative potential to the grids 50, 5| and 31, 38 but, on the contrary,a slow build-up of positive potential on these grids through condenser42, since the rectifier will provide an open circuit for current flowingother assessethan in the direction of. arrow 45'. It will be noted thatwhile the rapid collapse of current in transformer 46, between the laststage. of the amplifier and the detector, caused by the application ofthe negative bias to the. grids31 and 38, will put a negative charge onthe detector tubes 4'! and 48, this doesnot afie'ct the conditions ofthe receiving circuit sincethe tubes should be cut oif during signaltransmission. On the other hand, the slow increase of current curing'after the negative charge, is removed does notinduce a sufficientpotential in transformer 46 to affect the detector tubes in anys'ubstan: tial manner. In this way, no switches or other means arenecessary to cutout the'receiving ch.-

edit and the latter may therefore remain connected to the projectors atall times.

The receiving circuit from the projector I'.(Fig. 2) leads through thereceiving cable l3which can be traced through Fig. 3 to Fig-4, where theprojector potential is impressed upon theinput'transformer 49 in thereceiver amplifier It. The secondary of transformer 49 is connected tothe grids 52 and 53 of the tubes 50 and 51' in a tuned push-pullcircuit. This first stage, which is. of supersonic frequency butgenerally called" radio frequency amplification, is connected to thesecond stage including tubes 39 and 4'0 through a similar couplingtransformer 54. The signal, after being passed through the radiofrequency amplifier stages, is' similarly impressed by the transformer46 on the detector stage which includes tubes 41 and 48; These areconnected in push-pull with respect to the grids but in parallel withrespect to the plates.

The detector tubes are connected through an output circuit to a triggertube 55 which, through cable 56, operates a' discharge tube indicator51, and the marking stylus I! (Fig. 5). The stylus I1 is connectedthrough" the record sheet l-9 to ground. It will be noted that these twosignal devices 51' and I? are in series in theoutputcircuit of thetrigger tube 55; The arrangement'of the combination of the detectortubes, .48; and the tube 55 is in general similar to that which is usedin my prior 'Patent'No. 2,033,160. v

The output of the trigger tube 55 is also used to control the speed ofthe motor 1, establishing from time to time, through the electroniccontrolunit l6 the rate of rotation of the projector and the recorderassembly 22 of'F'ig. 1. For this purpose the output of tube-55 isconnected'to the primary of a transformer 58; The secondary 58a of thistransformer is connected by one terminal to a conductor 62 and by theother terminal to the other side of rectifier tube 44" whichpermitscurrent to flow only in onedirection,-that is; through the tubein such a way that current will always fiow in the direction of thearrow 6| in the conductor 62. The latter leads from Fig. 4 to'Fig. 5 upthrough a single pole, single throw switch 64, to the first positioncontact of pole 63d of a five-pole, four-position switch 63 which maybedesignated as the range switch. When this range switch is, for instance,in the position shown in Fig. 5, the'circuit continues through'amicroswitch 55 by way of v conductor 61, through switch blade63d,back'through Fig. 4 to Fig} 3. Here conductor 61 is connected to aseries-resistor 68, whence the circuitcontinues through the condenser69' and is completed through ground. I Condenser 69 is also connected tot:he;grid H of; vacuum tube 12; A'cross resistor-."fiB'lthere i lsconnected the grid circuit'of anot er-warren tube 13. The grid terminalor resistor 68 is con; nected to the grid 14 through series condenser15, while the other terminal of resistor 68 is connected to the cathodeof tube 13. A resistor. 16 is also provided directly between grid 14 andth cathode. Now since the current in the conductor 61 will flow in thedirection of the arrow 10, the grid ll of the highvacuum tube 12 willbecome negative with respect to ground when asignal impulse received andtriggers tube 55. For the same reason, the grid 14 of the tube 13 willalso bev made negative with respect to ground because of the directionin which the pulse goes through the resistor 68 as indicated by thearrow 10.

The charge on the condenser 69 will accumulate with successive signalpulses, the total charge from, time to time dependingupon the rate ofreceipt of signal pulses, as will appear below. This charge on thecondenser 69 acts to reduce the current through tube l2 since its grid Hbecome more negative with respect to its cathode which is at groundpotential. As will beseen later the function of tube 12 is to controlthe operation of the gaseous discharge tube 81 which directly determinesthe speed of motor I.

The function of tube 13 is to prevent the, discharge of condenser 69except in the circumstance where no signals are being received. To thisend, the tube 13 provides a means for the slow discharge of condenser 69only when signals stop. The anode of tube 13, it will be noted, isconnected to ground through a current limiting resistor. When tube 73 isconductive, it willtherefore' discharge condenser 69 through resistor68, tube 13 and its anode resistor. Tube 13-, however, remainsnon-conductive by grid rectification so long as signal pulses passthrough resistor 68 since condenser 15 is negatively charged thereby.This charge, however, slowly leaks off overresistance 16 so that if nosignals are being received, condenser 15 discharges makingtube l3conductive, gradually discharging condenser 69 and permitting tube 12 tobecome more conductive. The time constant of the grid circuit of tube 13is so chosen that, after two or three echoes have been missed insuccession, tube 13 will become conducting, thereby beginning thedischarge of condenser 69.

Now the anode ll of tube 12 is connected to the grid circuit of agaseous grid-controlled rectifier tube 81. The anode of this tubei'ss'upplied with alternating potential from transformers 88", whose centertap is' connected to ground at -92, whence the circuit is completed byway of groundedt'er minal 92d, conductor lllil to Fig. 2, where it isconnected to the armature 'lc athence'by conductor Hll'back to Fig. 3 tothe conductor 89-which is connected to the center tapoffilamenttransformer secondary i132 andthereby to the cathode of tube 81. 7

Between the grid and cathode of-tube 81 there is also applied aconstant, direct, positive voltage in series opposition to theback E. M.F. of motor I. This applied positive voltage at point 18maybe of theorder of 220 volts to ground-its chosen magnitudebeing determinedchiefly by the characteristics of motor 1. This voltage is derived fromthe plate transformer 88 and the full wave rectifier which includes thetubes I03 and I04 which are connected across theentire secondaryof'transformer 88. The cathodes of these rectifiers are connected acrossthe secondary lil5j-of afilamenttransformer [06. The center tapof thesecondary I05 leads through a'filter circuit I 01 and through fourparallel-connected vacuum tubes in circuit I08, which tubes may be ofthe type known as 2A3 and may have their filaments connected to thesecondary I09 of transformer I06. The grids of the four rectifier tubesare connected in the anode circuit of an amplifier tube H0, which may beof the type known as 6SJ7, whose cathode is connected to ground througha gaseous voltage regulator tube Ill. The circuit just described, whichis of conven tional design, produces a nearly pure direct voltage whichis very carefully regulated to maintain its value in spite of supplyline voltage variations.

Since the cathode of tube 81 is connected to transformer secondary I02whose center tap is grounded at 92a through the armature 1a of theprojector rotating motor, there is thus applied to the grid of tube 81the algebraic sum of a positive voltage from the D. C. source justdescribed and the armature back E. M. F.

A fourth voltage applied to the grid of tube 81 consists of a negativepulse applied periodically during the half cycles when the tubes anodeis positive. This negative pulse is obtained from the secondary 82 ofthe transformer 80 with the aid of a rectifier 83 which is connected inseries with it. Across the transformer and rectifier is a condenser H2and a resistor H3. This circuit is similar to that described in theapplication of William G. Gorton, 511,159, filed November 20, 1943, nowPatent No. 2,466,022, dated April 5, 1949. The voltage pulse produced onthe grid by this circuit decreases from a relatively high negative valueat the beginning of the positive half cycle of anode voltagesubstantially uniformly to the end of the positive half cycle to a valueat which the tube just barely remains inoperative.

It will be observed now that there are four voltages on the grid of tube81; first, the positive voltage supplied by the rectifier tubes I03 andH14, second, the motor back E. M. F., third, the negative voltage whichappears across resistor H3 as just described and, fourth, a negativevoltage dependent on the current flow through tube 12. The first threeof these voltages establish a certain speed for motor 1; the fourthvoltage determines whether the motor runs at that speed or slower orfaster.

In further consideration of this fourth voltage it will be noted that asthe grid 1| of the tube 12 r becomes more highly negative, less currentis passed through the tube so that the potential of the plate 11 riseswith respect to the applied direct current voltage at the point 18. Theincrease of the potential on the plate 11 thus increases relatively thepositive potential applied to the grid 19, through the connection madeto the resistance H3 at the point 8|.

There are thus applied to grid 19 voltages whose algebraic sumestablishes, during each alternating current cycle, the instant ofdischarge in the cycle of the triode 81. These discharge pulses areapplied to the motor 1 (Fig. 2), the armature of which, as previouslydescribed, is in series in the cathode-anode output circuit of the tube81.

When the charge on the condenser 69 continues to increase, the positivepotential at the point 8| will continue to rise (because current inplate circuit 11 decreases, thus decreasing the voltage drop acrossresistor H4, which drop opposes the positive voltage from point 18),placing continually a higher and higher positive potential on the grid19 of the tube 81 in such a manner that a greater amount of energy willbe supplied in each A. (2. cycle to the motor 1 to increase its speedand the speed of rotation of projector Under these circumstances, therange from which echoes can be received will decrease with an increasein the rate of receipt of incoming signals. Thus the distance at whichranging takes place is automatically adjusted as determined by theconstants of the circuit in such a manner that the distance ranged willcorrespond to the distance of a detected object from the observingstation while the object and the latter are approaching each other.

This is true even though the object and station are approaching at anincreasing rate or at a rate greater than that for which the circuitsare normally adjusted. In such cases the reflected signals will arriveat the projector in less than a full projector revolution, theprojectors directional characteristic being broad enough to permit this.Hence condenser 69 will accumulate a charge more rapidly, and cause theprojector to speed up more rapidly in its rotation.

On the contrary, when a detected object is receding, reflected signalswill soon cease being received. The charge on condenser 69 will not ofcourse increase. Under these conditions, the charge on the condenser 15which is continually leaking off through the resistor 16 will, within acertain time interval, depending upon the constants of its circuit,permit the negative charge to leak off of the grid 14 and thereby permitthe tube 13 to become conductive, under which conditions the chargeremaining on the condenser 69 will also begin to leak off. As thischarge begins to leak off, the negative potential on the grid 1| of thetube 12 decreases, more current flows through the tube, producing anincreased voltage drop across resistor ||4 opposing the applied positivepotential; and consequently, the positive potential at the point 8|lowers, which has the efiect of permitting less current to flow throughthe thyratron 81, and, therefore, slowing up the rotation of theprojector motor. As a result, therefore, if the signals are lost, therange will gradually increase either until a signal is again picked upor until the projector has slowed down in its rotational speed until themaximum range has been reached.

The maximum range is controlled by the effect of the state of charge ofthe condenser 89 upon another circuit. This circuit includes a gas tube93 having its control grid 94 connected to condenser 69, and its cathodeconnected through an adjustable potentiometer resistance 98 to ground92b. The resistance 98, which may be in series with other resistances,is also connected to point 18 at which there is a high positivepotential with respect to ground supplied from rectiflers I03, I04 aspreviously described. The cathode of tube 93 thus is at a certainpositive potential above ground. The anode of tube 93 is connectedthrough resistance 91 to the positive side of a separate D. C. supply atpoint 96. This D. C. supply circuit includes transformer H5 and a fullwave rectifier 6 having across its output a condenser H1 and a voltageregulator gas tube 95. The grid 1| of tube 12 is connected to thenegative side of this D. C. supply. Thus the anode circuit of triggertube 93 may be traced from positive potential point 96 to the anode oftube 93 through the tube to its cathode, through resistance 98 to ground92b, thence to the ground side of condenser 69, to grid 1|, to tube 95and back to point 96.

Now, when condenser 69 discharges, the bias on grid 94 of the triggertube 93 is permitted to go ll relatively positive, whereupon the'tubewill suddenly trigger and the positive potential applied across it fromthe point 95 will be applied to the condenser 69' which willthereupon'again become negatively charged to place a negative charge onthe grid II of the tube I2. This negative potential is such a highpotential that immediately the potential of the point 8|. goes back toits most positive point and the projector rotating motor 1 begins tospeed up very rapidly to reduce the range in an effort to catch themissing echoes. It will be noted, however, that during this operationthe condenser does not receiveany charge since the operation of the tube93 isnotthrough the resistor 68. Therefore, while the condenser 69 ischarged to a hig'hpotential, it immediately begins to leak off, through.tube E3, the rate of which maybe established so that after the projectormotor has established a minimum range of observation it will again beginto lengthen its range if no signal has been received. The minimum range(i. e. maximum speed of motor 1) is determined by the value of theresistor 91; the voltage drop' across this resistor and the chargeacquired by condenser 69 together determine the cutoff point of currentthrough tube 93 by reduction of anode voltage below the value requiredto maintain conduction. This leaves condenser 69; with a certain chargewhich begins to leak off. The speed of motor I thus attains a maxi- ,mumvalue, after which it again decreases. Of v course, when, a signal isreceived, a pulse again appears across the resistor'68 and a negativebias is again established on the grid '14 stopping the leak anddischarge of the condenser 69 as previously described.

It will thus be apparent that in the system as so far described, whenthe switches are set for automatic ranging, the projector will rotate ata certain maximum speed whereby ranging will be carried out at acorrespondingly minimum distance from the vessel; then the projectorwill gradually decrease its speed of rotation whereby the rangingdistance decreases until a certain minimum motor speed and maximumranging distance are attained.v Still assuming no' echoes arereceived,the projector will then automatically increase its speed to amaximum and repeat the process. If at anytime a signal is received whichhas been reflected from some object in the field, the speed of rotationof theprojector will auto- -matically change to keep the rangingdistance equal to the distance of the object until the object has movedoutside of the maximum or minimum ranging distances.

Automatic ranging in this manner is however useful only'in; the forwardsector when the ship is in motion, although it can be used in the aftsector when" the ship isstationaiy. This is due to the fact thatthe'noise of the ships propeller fronrthe aft sector is always much moreintense than any refiectedsignal so that the automatic ranging systemwill not work aft of the vessel when the ship is underway. The rangeswitch 63, Fig; 5, has four positions, three for rangin and one forsimplelistening. The extreme left position isv for ranging forward, thesecond position 15 forranging. fore and aft, the third position is forranging art and the fourth position is for listening. Since automatic.ranging cannot be used aft or fore and aft when'the ship is underway,il*have provided which automatically make it impossible for theoperator to use automatic ranging in these two switch positions when theship is under way, but which on the other I2 hand do make it possiblefor the operator to carry out ranging by manually adjusting the motorspeed and thereby the distance at which ranging takes place.

It will be observed from the diagram in Fig. 5 that with the rangeswitch 63 in position one, which is for ranging forward of the vessel,the microswitch 65' is short-circuited by switch arm 63d. However, forall other positions of range switch 63, that is for ranging fore and aftor ranging aft only, microswitch 66 is in series in the control circuit.This switch 66 is normally open but it is closed mechanically when thepaper feed control I20 is set to correspond to zero ships speed. Whenswitch 66 is open, switch 63 being in second or third positions, it willbe observed that conductors B2 and 61 will be open so that the circuitof trigger tube 55 in the receiver amplifier, Fig. 4, will not beconnected to the control unit I6; therefore the charge on condenser 69,the operation of gas tube 81 and the speed of motor I will not beaffected by returning echoes.

The speed of motor I is, on the contrary, controlled by the operatormanually by means of potentiometer I I9 in Fig. 5. The voltage suppliedby this is applied through conductor IZI, switch arm 63b of switch 63,and conductor I22 to the diode I23 in Fig. 3. Current will flow throughthe diode I23 when the voltage across output tube minus the potentialacross the condenser 69 is greater than the voltage set on the controlpotentiometer H9. The condenser 69, therefore, reaches a substantiallyconstant state of charge, depending upon the adjustment of potentiometerI I9 and the rate of leakage through tube 13. It will be observed thatsince the diode I23 is conductive in only one direction, the presence ofthe manual speed control potentiometer H9 hasno effect upon the circuitwhen the system is set for automatic ranging. It will also be observedthat even when switch63 is set for ranging in the forward sector only,it ispossible for the op-' erator to cut out the automatic rangingfeature andto control the speed of rotation of the prO- jector manuallysimply by opening the switch Be in Fig. 5. g

One feature of the system which has not yet been discussed is anautomatic sensitivity control whereby the system is automaticallyconditioned to receive only signals which have an intensitysubstantially the same as the last previously received signal. By meansof this arrangemerit most extraneous noises can be eliminated from thereceiving circuit so that they will not affect the automatic rangingsystem. For the purposes of this automatic sensitivity control there isprovided in the receiver amplifier, Fig. 4, in the detector tube stage,a source of grid bias by means of a condenser I24 which is connectedbetween the center tap of the secondary of the detector :inputtransformer 46 and ground. In shunt with this condenser is a leakresistance I25. The values of condenser I24 and resistance I25 are sochosen that the circuit will have a timev constant such that the chargeon condenser I24 will leak off at a slow rate. In the circuit shown thecondenser may, for example, have a capacity of one microfarad whiletheresistance I25 may be of the order of 20 megohms. It will be evidentnow that incoming signals will cause a potential to build up graduallyon condenser I24. The condenser will eventually reach a potential whichis determined by the intensity of incoming signals and the rate of dis sf e Of he condenser through resistance I25.

The charge on the condenser is applied negatively to the grids of bothdetector tubes 4'! and 48. By this means the detector tubes can passcurrent only when Signals are received which have a larger potentialvalue than the bias provided by condenser I24. Consequently thestrongest signal in the field from time to time will set the value ofthis grid bias and weaker signals will not operate the recorder or theindicator. If however the reflecting object should move farther away sothat the reflected signals become of lesser intensity, the reflectedsignal may be missed during one excursion of the projector but by thetime of its next excursion the charge on condenser I24 will have beenreduced so that the reflected signal wi1l again appear. An automaticsensitivity control circuit of this type is more fully described in myPatent No. 2,108,090, dated February 15, 1938.

A manually operated sensitivity control is also provided in thepotentiometer I26, Fig. 5, which through conductor I21 provides abiasing potential on the input stage 50, of the amplifier, Fig. 4.Mechanically coupled to the sensitivity control I 26 is a switch I28which ,is normally closed on contact I29 but which is open when thesensitivity control I28 is moved to the position of full sensitivity. Itwill be noted that the terminal I29 of switch I28 is connected byconductor I30 to the center tap or the secondary of the detector inputtransformer 46, namely, the same point to which the automaticsensitivity control time delay circuit I24, I is connected. Thus whenswitch I28 is closed, this point is grounded so that the automaticsensitivity control is inoperative when manual sensitivity control isbeing used. The automatic sensitivity control is also inoperative whenthe ranging switch is set for ranging fore and aft and for ranging aftwhen the ship is under Way. This is determined by microswitch I3I, Fig.5, which is connected in parallel with switch I28. The condition ofswitch I3I is determined by the paper feed speed control I20, such thatthe switch is normally closed, thereby cutting out the automaticsensitivity control, unless control I20 is adjusted for zero shipsspeed. It will also be noted that the switch I3I is connected into thesystem through range switch pole 630. Thus the switch I3I is operativeonly when the range switch 63 is set for ranging fore and aft or aft.The reason for making the automatic sensitivity control inoperative inthese switch positions is that the propeller noise arriving from aft ofthe vessel when the ship is under way would always be of sufiicientintensity to set the bias on condenser I 24 so that the automaticsensitivity control could not function when ranging aft. My automaticsystem therefore makes it impossible to use automatic sensitivitycontrol when ranging aft.

The fourth position of range switch 63 is for listening to the noisesmade by objects to be detected. It will be understood that when rangeswitch 63 is set in this fourth position no signals are sent out by theprojector but the projector is always in a condition to receive signalsduring its entire rotation. The speed of rotation for listening is fixedby means of resistor I32, Fig. 5, which is connected to the fourthposition of second pole 63b of range switch 63. Thereby, throughconductor I22 and rectifier tube I23, a fixed charge is accumulated oncondenser 69 whereby the operating conditions of tube 81 are fixed andthe motor I runs at a fixed speed. This 14 speed is adjusted to a valuewhich will bring the stylus I I of the recorder I5 into a position onthe recording paper along a circle approximately midway between thecenter and the outside of the record.

Since the relation of the speed of rotation of the projector and theranging distance is an equilateral hyperbola, the record paper isarranged to be moved continuously through the recorder at a speed whichis an inverse square function of the speed of rotation of the projectorand is further manually adjustable in accordance with the speed of theobserving vessel. This makes possible an accurate calibration of therecord at all ranging distances and at all ships speeds.

The paper is drawn through the recorder by a motor I35, Fig. 5. Thefield I35 of the paper feed motor is supplied with a D. C. voltage whichvaries inversely with the speed of rotation of the projector I. For thispurpose, field winding I35) is connected across two voltages inopposition to each other. One is a fixed voltage derived from theregulated power supply (Fig. 3) and the other is the voltage across thearmature of motor I. Thus the circuit of field winding may be tracedfrom the field winding I35f through conductors I 8| and IOI across themotor armature 1a, the return connection being made by way of conductorI00, ground 92a, Fig. 3, ground I90 in the power supply, Fig. 3, to thepoint I8; thence by conductor I9I to the field resistance I83 and backto the field winding I35f. Since the power supply voltage is alwayshigher than the voltage across armature 1a, the strength of the field inmotor I 35 varies inversely with the speed of motor 7 whereby the speedof motor I35 also varies inversely as the speed of motor I.

The armature I35a is connected by conductors I36 and I3'I to the outputof gaseous triode I38. This circuit may be traced from the armatureI35a, Fig. 5, conductor I31 to Fig. 3 to the center tap of filamenttransformer secondary I39 through the tube I38 to the ground 92, thenceto the ground 92a and back through conductor I36 to the armature I 35a.Fig. 5. The grid I40 of tube I38 has three voltages applied to it. Thefirst voltage consists of a negative pulse periodically applied duringthe positive half cycles of anode potential. This negative pulse isobtained from the secondary I II of the transformer in combination witha rectifier, condenser and resistor in the same manner as for thecorresponding circuit previously described for the gaseous triode 81. Apositive controlling voltage is also applied to the grid I 40. Thisvoltage is the difference between a portion of the voltage acrossarmature Ia and a voltage obtained from potentiometer I20 (Fig. 5) whichis manually adjustable in proportion to ships speed. Here, too, thearmature Ia voltage is smaller than the potentiometer voltage, so thatagain the speed of motor I35 varies inversely as the speed of motor 1.Consequently the resultant speed of motor I35 varies inversely as thesquare of the speed of motor 7.

Potentiometer 208 (Fig. 5) controls the intensity of indicator lights I84 and 2 II used in the recorder I5. The projector keying switches 2I3and 2I4 are operated by the recorder mechanism, as is set forth moreparticularly in the aforementioned parent application. Switch 2 I3 isthe keying switch. This switch connects the projector to the powersupply during one half of its revolution whereby the projector transmitsa beam of compressionalwaves provided the range switch 63 is 'in itsfirst position for ranging'for ward. I v a As shown diagrammatically inFig. 1, the recorder I is provided with a cam 2l2 which has a .raisedportion extending over half its circumference A cam follower 2I2' rideson the cam 2|.2 and operates the keying switch 23, corresponding to theswitch 2l3 in Fig. 5. By means oi switch 2M, the projector is caused toperform one complete echo ranging cycle forward of the .beam and then torepeat aft of the beam alterinately-soas to .cover 360 in two steps of180 .each. This is done by transmitting from bearing 270 to bearing 90subsequently receiving on the next half revolution on these samebearings with the other half of the projector; then with the elapse of ahalf revolution, during which neither transmission nor reception takesplace, repeating the procedure outlined above on. bearing 90 to .'270thus covering 360 in two steps when the range switch 63 is set in itssecond position for ranging both fore and aft.

What is claimed is:

.1...In.combination with a means for producing .electrical impulses inresponse to substantially periodically repeated phenomena, an electricmotor, and a gaseous grid-controlled rectifier tube circuit having itsanode-cathode path connected in the electriccurrent supply path to saidmotor I for controlling the speed of said motor including 1 a condenser,means for impressing said impulses ,upon said condenser to charge thesame, a vacuum tube having a control grid, means impressing the chargeon said condenser upon said grid, means impressing a direct positivecontrol voltage upon the grid of said rectifier and in oppositionthereto a voltage proportional to the current now .through said vacuumtube.

2. In combination with a means for producing electrical impulses inresponse to substantially periodically repeated phenomena, an electricmotor, means including a grid-controlled electron tube havingits'anode-cathode path'ser'ially charged to one value and graduallydischarged to another value and thereby causes said motor to operate ataconstantly varying speedbetween limits including a speed which saidimpulses when present cause said motor to assume.

A. An arrangement as in claim 1 including means operative, in theabsence of said impulses, to cause said condenser to be graduallydischarged to cause said motor to run at an increasingly slow speed, andmeans to periodically recharge said condenser to'cause said motor to runat a prescribed high speed. V

. 5. An arrangement as in claim 4 including means responsive to thepresence of said pulses to prevent the operation of said periodicallyrecharging means.

' EDWIN E. TURNER, JR.

REFERENCES omen The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date. '2 ,137,071 Young ',Nov. 15,1938 2,399,421 Artzt Apr. 30, 1946

